冲入法球化处理过程模型探讨

提出了新的球化反应过程模型：球化剂是层状融解的，球化反应的快慢在一定温度条件下是由与铁水接触的球化剂的量决定的。

TC17钛合金热变形过程中片状组织演变规律

通过等温锻造试验和有限元模拟,研究了TC17钛合金在α+β两相区变形过程中热加工工艺参数对显微组织演变的影响规律。通过组织观察分析发现:随着变形程度和变形温度的增加,TC17钛合金中的片层组织逐渐向球化组织转变。变形量对片状组织的球化起决定作用,当变形量为小于20%时,仅有少数片状α相发生了弯折或扭曲,球化现象不明显;随着变形量的增加,片状组织被不同程度的弯曲、破碎,球化程度随着变形量的增加逐渐变大。变形温度对球化过程也起一定的作用,随着变形温度的升高,球化效果越来越明显,这与较高的变形温度会提高位错或原子的迁移能力使片状组织有足够的能量通过界面迁移实现断裂、球化有关。

固溶处理对Mg-2Zn-3Y合金组织和性能的影响

为了研究固溶处理对铸态Mg-2Zn-3Y合金组织和性能的影响,采用光学显微镜、X射线衍射仪、扫描电子显微镜、拉伸试验机和维氏硬度计对固溶处理后的合金进行了组织分析及性能测试.结果表明:Mg-2Zn-3Y合金中含有LPSO相和W相,随着固溶温度的升高,块状LPSO相区域逐渐出现层片状形貌,W相发生球化、粗化和重熔现象,合金的抗拉强度、屈服强度、伸长率和硬度均呈现先升高后降低趋势;经450℃固溶12 h后,合金的强化效果最佳,抗拉强度为187 MPa,屈服强度为107 MPa,伸长率为8.0%,硬度为82.5 HV.

Key nitrogen biogeochemical processes revealed by the nitrogen isotopic composition of dissolved nitrate in the Changjiang River estuary, China

Seasonal variations in the nitrogen isotopic composition of dissolved nitrate （δ15NO3） were investigated in the surface waters of the Changjiang River estuary in 2009 and 2010. δ15NO3 varied between -4.6‰ and 8.9%0 with changes in temperature, salinity, dissolved oxygen concentrations, and the composition of the dissolved inorganic nitrogen pool. In February, biological processes decreased because of low temperature, and the mean δ15NO3 near the river mouth was 2.4%0. In May, δ15NO3 was the highest in the surface waters among all seasons. Analysis on the conservative mixing revealed assimilation, and this finding is supported by positive relationship between Chl a and δ15NO3. The fractionation factor of assimilation was estimated to be 2.0‰ by the Rayleigh equation. Nitrification was supported based on the mixing behaviors in November 2010 and the low δ15NO3 values in May and November 2009. The high ammonium concentrations in the adjacent marine area and positive relationships between total organic nitrogen and δ15NO3 in November 2010 indicated that mineralization was taking place.

BIOGEOCHEMICAL PROCESSES OF PHOSPHORUS AND SILICON IN SOUTHERN BOHAI SEA SURFACE SEDIMENTS

Based on the author’s previously obtained results on P and Si forms in southern Bohai Sea surface sediments,this study mainly foucusing on the controlling factors, existence forms, and biogeochemical processes of P and Si showed that the transferable forms of phosphorus in sediments were mainly controlled by the mineralization of organic matters and the reduction of high valence iron; whereas the transferable forms of silicon were possibly controlled by the dissolution and precipitation as well as biochemical processes of living organisms.

Behavior of rare earth elements in granitic profiles, eastern Tibetan Plateau, China

Rare earth elements(REEs) can record geologic and geochemical processes. We studied two granitic regolith profiles from different climatic zones in eastern Tibetan Plateau and found that(1)∑ RREEs ranged from119.65 to 275.33 mg/kg in profile ND and5.11–474.55 mg/kg in profile GTC, with average values of205.79 and 161 mg/kg, respectively. ∑RREEs was higher in accumulation horizon and semi-regolith;(2) Influenced by climate, the fractionation of light and heavy REEs(LREEs and HREEs) varied during weathering. The ratio of LREEs/HREEs in pedosphere was higher than semi-regolith in tropical profile;(3) A negative Eu anomaly in both profiles was the result of bedrock weathering. A positive Ce anomaly was observed in all layers of profile ND, and only in the upper 100 cm of profile GTC. This indicates that redox conditions along the regolith profile varied considerably with climate.(4) Normalized by chondrite,LREEs accumulated much more than HREEs; REE distribution curves were right-leaning with a V-type Eu anomaly in both profiles.

Crystals of suspended marine barite in the eastern equatorial Pacific:processes of dissolution and effects on crystal morphology

Suspended particulate substances were sampled in the eastem equatorial Pacific in water column from surface to near bottom in five stations in 2005, from which 868 barite crystals were recovered. The barite crystals were examined under scanning electron microscopy. About 61% of the total barites crystals contained detectable Sr by energy dispersive X-ray spectrometry. Barite crystals could be classified into four groups based on their morphology： 1） bladed; 2） ovoid or rounded; 3） arrow-like; and 4） irregularly shaped. The arrow-like barite crystals in natural environment has never been reported before. In addition, about a half of the studied crystals showed features of dissolution as cavities or holes inside of the crystals or around their edges. We found that differential dissolution of barite crystals is consequence of heterogeneous Sr distribution in barite crystals. Our results would help in understanding the biogeochemical processes of marine barite formation and preservation in seawater and marine sediments.

Effects of slope position and land use on the stability of aggregateassociated organic carbon in calcareous soils

Topography and land use affect soil organic carbon(SOC) storage, stabilization, and turnover, through several biogeochemical processes. This study investigated the aggregate composition and SOC content of bulk soils and aggregates at different slope positions under different land uses in a typical karst catchment of southwestern China. Our results show that the proportion of macro-aggregates and the SOC content of bulk soils and aggregates at different slope positions decreased from the upper to the lower slope. The SOC content generally increased with an increase in the mean weight diameter and proportion of macro-aggregates under different land uses. Our results indicate that macro-aggregates in forest and grassland soils make a greater contribution to both aggregate composition and SOC content than that in arable land soils. Therefore,converting farmland to forest or grassland can facilitate the accumulation of macro-aggregates as well as the storage of SOC.

Phosphorus Biogeochemical Cycle Research in Mountainous Ecosystems

Phosphorus(P),as a limiting nutrient,plays a crucial role in the mountainous ecosystem development.Its biogeochemical cycle in mountainous ecosystems determines the bioavailability and sustainable supply of P,and thus becomes a crucial process which needs to be fully understood and described for ecological and environmental conservation.However,most of research about P biogeochemical processes has been carried out in aquatic environment and agronomic field,but rare researches have been done in mountain ecosystem.In the present review,we summarize researches on P biogeochemical cycle concerning mountain ecosystem in recent decades,including rock weathering,the release,transformation and bioavailability of P,interactions between the P biological cycle and microbial and plant life,as well as the development of models.Based on the state of art,we propose the future work on this direction,including the integration of all these research,the development of a practical model to understand the P biogeochemical cycle and its bioavailability,and to provide a reference for ecological and environmental conservation of mountainous ecosystems and lowland aquatic systems.

Water Chemistry and Hydrometeorology in a Glacierized Catchment in the Polar Urals,Russia

This study aims to determine the relationships between local meteorological conditions,proglacial river discharge and biogeochemical processes operating in a periglacial basin located in the Polar Ural mountain range, Russia. Fieldwork was conducted in the catchment of Obruchev Glacier(13 km2) during the summer peak flow period in 2008. River discharge was dominated by snowmelt and changed from 3300 l s-1 to less than 1000 l s-1. The mean daily air temperatures of stations situated in the mountain tundra and near Obruchev Glacier from July 11 th to August 1st 2008 were 14.4°C and 10.3°C, respectively. The glacial river had low total dissolved solids varying from 4.5 to 9 mg l-1 and coefficients of correlation between Na+ and Cl-, K+ and Cl-, as well as NH4+ and Cl- were 0.94, 0.90 and 0.84, respectively. Rainfall events affected the snowmelt initiation and provided an essential part of the discharge during the intense snowmelt period, which occurred from July 11 th to July 18 th 2008. Data showed that Na+ and K+ in the surface water derived from snowmelt rather than chemical weathering of silicates. Also, it was obtained that NO3- derived from the melting snowpack, whereas ammonification occurring under the snowpacks was the primary source for NH4+.

Water Analysis for Heavy Metals Content in Selected Boreholes in Port Harcourt Metropolis （A Case Study during 2010-2011）

Underground water （Borehole） has been the main alternative source of drinking water for most communities in my country. Previous studies have revealed high levels of contamination. The origin of which can be attributed to geochemical processes, combustion of fossil fuels, mining and anthropogenic activities. Most borehole water and well water in local communities of Nigeria are not safe for drinking due to heavy industrial and environmental pollution. This study was undertaken to assess the quality in some selected boreholes in the Port Harcourt metropolis for a period of two years. Borehole water samples were randomly collected from thirteen boreholes in a local community in plastic bottles （100 mL） in the months of September for the years of study （2010 ＆ 2011）. Four out of the seven heavy metals analyzed were found to be present in the first year of study. These were Fe, Cu, Mn and Zn. In the second year of study, Pb, Cr, Fe and Co were not detected in all of the samples except Cu and Fe which were present in only two samples. Mn and Zn were found to be present in all of the samples for both years of study.

Heavy metal content in coral reef sediments from Red Sea of Yemen and its significance on marine environment

In order to determine and assess the concentrations of trace elements in coral reefs sediments from Red Sea of Yemen, sediment samples were collected, treated and analyzed for cadmium, chromium, cobalt, copper, manganese, nickel, lead, iron, zinc and vanadium by the atomic absorption spectrometric analysis. The result is that cadmium, cobalt and lead concentrations were high and other elements are low or the same as natural background. It is concluded that the high cadmium, cobalt and lead levels in coral reefs sediments will have negative effects on marine life of the sites, so further researches are needed to characterize the sources fate, biogeochemical processes and impacts of these trace elements on coral reefs and marine of the region.

Mathematical models and expert system for grate-kiln process of iron ore oxide pellet production.Part Ⅱ:Rotary kiln process control

Rotary kiln process for iron ore oxide pellet production is hard to detect and control.Construction of one-dimensional model of temperature field in rotary kiln was described.And the results lay a solid foundation for online control.Establishment of kiln process control expert system was presented,with maximum temperature of pellet and gas temperature at the feed end as control cores,and interval estimate as control strategy.Software was developed and put into application in a pellet plant.The results show that control guidance of this system is accurate and effective.After production application for nearly one year,the compressive strength and first grade rate of pellet are increased by 86 N and 2.54%,respectively,while FeO content is 0.05% lowered.This system can reveal detailed information of real time kiln process,and provide a powerful tool for online control of pellet production.

Microaerobic iron oxidation and carbon assimilation and associated microbial community in paddy soil

Iron oxidation is a prevalent and important biogeochemical process in paddy soil,but little is known about whether and how microbially mediated iron oxidation is coupled with carbon assimilation,particularly under microaerobic conditions.Here,we investigated kinetics of CO_2 assimilation and Fe(Ⅱ)oxidation in an incubation experiment with paddy soil under suboxic conditions,and profiled the associated microbial community using DNA-stable isotope probing and 16S r RNA gene-based sequencing.The results showed that CO_2 assimilation and Fe(II)oxidation in the gradient tubes were predominantly mediated by the microbes enriched in the paddy soil,primarily Azospirillum and Magnetospirillum,as their relative abundances were higher in the^( 13)C heavy fractions compared to^( 12)C heavy fractions.This study provided direct evidence of chemoautotrophic microaerophiles linking iron oxidation and carbon assimilation at the oxic–anoxic interface in the paddy soil ecosystem.

An Experimental Study on Major Element Release from the Sediments in the Changjiang(Yangtze River) Estuary

With the enhanced warming and acidification of global ocean, whether and to what extent the naturally-weathered flu- vial sediment into the sea can release elements and thus influence the geochemical process and ecosystem of global ocean remain to be resolved. In this contribution, an experimental study was carried out to examine the release rates of major elements （Ca, K, Mg and AI） from the surface sediments in the Changjiang （Yangtze River） Estuary under the pH values of 4.0, 6.0 and 7.0. The two stud- ied sediments consist primarily of quartz, plagioclase, calcite and clay minerals, with the BET （Brunauer, Emmett and Teller） surface areas of 61.7m2g-1 and 23.1 m2g-1. Major elements of Ca, K, Mg and A1 show different release rates under different solution pH values. With the decreasing solution pH, the release rates of Ca and K increase obviously, while the release rates of Mg and A1 in- crease with the initial solution pH varying from 6.0 to 7.0. The different release rates of these elements are closely related to the original mineral composition of the sediments and the reaction kinetics. Based on the experimental observation, quartz and clay min- erals that have low dissolution rates may dominate the major element release to the aqueous phase. This study reveals that the en- hancing ocean acidification could cause considerable release of major elements from natural terrigenous sediments into the ambient marine environment, which has to be considered carefully in the future study on global change.

Radionuclides and mercury in the salt lakes of the Crimea

^99Sr concentrations, resulting from the Chernobyl NPP accident, were determined in the salt lakes of the Crimea （Lakes Kiyatskoe, Kirleutskoe, Kizil-Yar, Bakalskoe and Donuzlav）, together with the redistribution between the components of the ecosystems. The content of mercury in the waters of the studied reservoirs was also established. Vertical distributions of natural radionuclide activities （^238U, ^232Th, ^226Ra, ^210pb, ^40K） and anthropogenic ^137Cs concentrations （as radiotracers） were determined in the bottom sediments of the Koyashskoe salt lake （located in the south-eastern Crimea） to evaluate the long- term dynamics and biogeochemical processes. Radiochemical and chemical analysis was undertaken and radiotracer and statistical methods were applied to the analytical data. The highest concentrations of ^99Sr in the water of Lake Kiyatskoe （350.5 and 98.0 Bq/m^3） and Lake Kirleutskoe （121.3 Bq/m^3） were due to the discharge of the Dnieper water from the North-Crimean Canal. The high content of mercury in Lake Kiyatskoe （363.2 ng/L） and in seawater near Lake Kizil-Yar （364 ng/L） exceeded the maximum permissible concentration （3.5 times the maximum）. Natural radionuclides provide the main contribution to the total radioactivity （artificial and natural combined） in the bottom sediments of Lake Koyashskoe. The significant concentration of ^210pb in the upper layer of bottom sediments of the lake indicates an active inflow of its parent radionuclide-gaseous ^222Rn from the lower layers of the bottom sediment. The average sedimentation rates in Lake Koyashskoe, determined using ^210pb and ^137Cs data, were 0.117 and 0.109 cm per year, respectively.

Rock chemical weathering by sulfuric acid: pathway, method and prospect

To investigate the role of sulfuric acid-based carbonate weathering in global CO_2 sequestration of climate changes, we systematically discussed the pathway of sulfuric acid in rock chemical weathering and its feedback mechanism for global warming. We showed the methods used to determine the accurate amount of sulfate flux,accounting for the sulfuric acid resulted from sulfide oxidation. Finally, we pointed out some prospects for further detailed work on the exact calculation of the sulfate fluxes for the CO_2 net-release.

Difference between CKD-EPI and MDRD equations in calculating glomerular filtration rate in patients with cirrhosis

AIM:To evaluate the difference between the performance of the (CKD-EPI) and Modification of Diet in Renal Disease (MDRD) equations in cirrhotic patients. METHODS: From Jan 2004 to Oct 2008, 4127 cirrhotic patients were reviewed. Patients with incomplete data with respect to renal function were excluded; thus, a total of 3791 patients were included in the study. The glomerular filtration rate (GFR) was estimated by the 4-variable MDRD (MDRD-4), 6-variable MDRD (MDRD-6), and CKD-EPI equations.RESULTS:When serum creatinine was 0.7-6.8 mg/dL and 0.6-5.3 mg/dL in men and women, respectively, a significantly lower GFR was estimated by the MDRD-6 than by the CKD-EPI. Similar GFRs were calculated by both equations when creatinine was > 6.9 mg/dL and > 5.4 mg/dL in men and women, respectively. In predicting in-hospital mortality, estimated GFR obtained by the MDRD-6 showed better accuracy [81.72%; 95% confidence interval (CI), 0.94-0.95] than that obtained by the MDRD-4 (80.22%; 95%CI, 0.96-0.97), CKD-EPI (79.93%; 95%CI, 0.96-0.96), and creatinine (77.50%; 95%CI, 2.27-2.63). CONCLUSION: GFR calculated by the 6-variable MDRD equation may be closer to the true GFR than that calculated by the CKD-EPI equation.

A new two-dimensional experimental apparatus for electrochemical remediation processes

Electrochemical extraction of contaminants from soils is a promising soil decontamination technology. Various experiments have been conducted to study electrochemical reactions and geochemical processes in the electrochemical extraction using different experimental apparatuses. This paper presents the development of a new closed two-dimensional(2D) apparatus that can better simulate the field application of the technology and accurately monitor the most important electrochemical parameters to understand the process. The innovative features of the new apparatus include the outer and inner electrodes designed to apply a non-uniform electrical field across the specimen as in the field electrochemical remediation process, the probes installed to measure the 2D distribution of electrical voltage, and the gas and fluid volume measurement devices used to accurately monitor the gas generation and electroosmotic flow rates at both electrodes as a function of time. The components of this new apparatus and the features of each component are described. The operating procedure and some typical results from three experiments with the apparatus are demonstrated. The results show that the variation of the gas generation rate is in good agreement with the electric current. Their relation provides a valid evaluation for electrochemical behavior of the system and Faraday's laws of electrolysis. The 2D profiles of cadmium concentration and voltage distribution at the end of the experiment reveal the great effects of a non-uniform electrical field on the contaminant mobilization.

The role of extracellular matrix in age-related conduction disorders： a forgotten player？

Cardiovascular aging is a physiological process gradually leading to structural degeneration and functional loss of all the cardiac and vascular components. Conduction system is also deeply influenced by the aging process with relevant reflexes in the clinical side. Age-related arrhythmias carry significant morbidity and mortality and represent a clinical and economical burden. An important and unjustly unrecognized actor in the pathophysiology of aging is represented by the extracellular matrix （ECM） that not only structurally supports the heart determining its mechanical and functional properties, but also sends a biological signaling regulating cellular function and maintaining tissue homeostasis. At the biophysical level, cardiac ECM exhibits a peculiar degree of anisotropy, which is among the main determinants of the conductive properties of the specialized electrical conduction system. Age-associated alterations of cardiac ECM are therefore able to profoundly affect the function of the conduction system with striking impact on the patient clinical conditions. This review will focus on the ECM changes that occur during aging in the heart conduction system and on their translation to the clinical scenario. Potential diagnostic and therapeutical perspectives arising from the knowledge on ECM age-associated alterations are further discussed.